Basis of Presentation - Narrative (Details) - USD ($)		3 Months Ended		9 Months Ended
	Oct. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net tax benefit recorded for changes in estimates		$ 132,000,000		$ 305,000,000
Increase to noninterest revenue		13,352,000,000	$ 12,780,000,000	42,215,000,000	$ 39,178,000,000
Increase to noninterest expense		15,623,000,000	14,570,000,000	47,674,000,000	44,620,000,000
Impact to net income		8,380,000,000	6,732,000,000	25,408,000,000	20,209,000,000
Increase in cash and due from banks		23,225,000,000		23,225,000,000		$ 25,898,000,000
Increase in deposits with banks		395,872,000,000		395,872,000,000		405,406,000,000
Decrease in other assets		$ (115,936,000,000)		$ (115,936,000,000)		(113,587,000,000)
Subsequent Event | Non-cumulative Perpetual Preferred Stock, Series I
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Redemption of fixed-to-floating rate stock	$ 1,700,000,000
Accounting Standards Update 2014-09 | Revisions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase to noninterest revenue			252,000,000		777,000,000
Increase to noninterest expense			252,000,000		777,000,000
Impact to net income			$ 0		$ 0
Accounting Standards Update 2016-18 | Revisions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in cash and due from banks						71,000,000
Increase in deposits with banks						1,100,000,000
Decrease in other assets						$ 1,200,000,000